The present invention relates to a method of improving the control behavior of an anti-lock control system, in particular, of improving the steerability of the automotive vehicle and the driving stability during cornering, wherein a vehicle reference speed is derived from the rotating behavior of the vehicle wheel s and criteria are obtained for identifying a cornering situation and the curve direction, and once a cornering situation is identified, the standard control mode is replaced by a special or curve control mode which already in the partial deceleration range causes a reduction in brake pressure on the front wheel at the inner side of the curve and/or on the rear wheel at the inner side of the curve.
During cornering is identified, a stabilizing yaw moment about the vertical axis of the vehicle that compensates for cornering is produced in a control method of the above-mentioned type by relieving the wheels at the inner side of the curve from pressure. The brake pressure on the wheels at the outer side of the curve is maintained constant when the control commences during a partial braking operation, or increases automatically by interrupting further brake pressure increase on the wheel(s) at the inner side of the curve.
DE 34 13 738 C2 discloses an anti-lock control system provided with a system for identifying a cornering situation also based on wheel slip measurement. To identify a cornering situation, the slip values on the wheels at one vehicle side are summed up and compared to the slip values on the wheels at the other vehicle side, generating a cornering identification signal as soon as the difference of the summed-up slip values exceeds a predetermined threshold value. Upon identification of a cornering situation, selection criteria, such as "select-low" or "select high" according to which the course of pressure in the individual brake pressure control channels of the said brake system is controlled, and threshold values for rendering the said selection criteria effective, are varied. In this way, the control will be adjusted to the varying conditions during straight-forward driving and during cornering.
DE 21 19 590 A1 teaches generating a cornering identification signal with the aid of a lateral accelerometer, such as a mercury switch.
Moreover, it is already known in the art to extend the functions of an anti-lock control system by employing the system for improving the driving stability or deceleration stability in a curve. For this purpose, during cornering or during a partial deceleration, i.e., in a deceleration process in which the threshold of response to the anti-lock control system is not achieved, a stabilizing moment about the vertical axis of the vehicle is created by specifically delaying the brake pressure build-up on the wheels at the inner side of the curve compared to the brake pressure on the wheels on the outer side of the curve ("Bremsanlage und Schlupf-Regelsystem der neuen 7-er Reihe von BMW" (Brake System and Slip Control System of the new BMW No. 7 series); ATZ 97 (1995), pp. 8-15, and "Bremsanlage und Schlupf-Regelsysteme der neuen Baureihe 5 von BMW" (Brake System and Slip Control Systems of the new BMW No. 5 series); ATZ 98 (1996), pp. 188-194. The information on the actual steering angle is derived--if no steering angle sensor is used--from the lateral acceleration which, in turn, is calculated from the wheel sensor signals.
It is an object of the present invention to ensure, in a method of the above-mentioned type, that a shortest possible stopping distance can be achieved in all cases, i.e., also in situations which might be affected by the special control mode. One objective is to avoid the occurrence of an extension of the necessary stopping distance as a result of the special control mode which, in terms of its principle, causes a reduction of the brake force on the wheels at the inner side of the curve.